BACKGROUND The field of mHealth has grown exponentially in the last decade due to the widespread use of smartphones and the advancements in mobile technology, which has created opportunities to find solutions to unmet healthcare needs for patients with chronic diseases. Furthermore, healthcare is entering a new value-based paradigm, founded on three main pillars: efficiency, safety, and value for patients. OBJECTIVE The objective of this study is to evaluate the effectiveness of mHealth interventions in the treatment of BC, considering factors such as the duration of the intervention, the type of intervention, the patient subtype, and the analyzed outcomes. The study aims to identify which mHealth interventions are more effective for treating BC in different patient subtypes, and how these interventions affect clinical outcomes in terms of symptom improvement, and quality of life. METHODS Three databases were systematically searched to identify studies that met eligibility criteria: PubMed, PsychInfo, and Google Scholar. Inclusion criteria were: evaluation of the use of mHealth in cancer patients, at least 30 participants with breast cancer, randomized control trials or prospective pre-post studies, inclusion of PROs, QoL or other determinants of health as primary outcomes, minimum duration of intervention of 8 weeks, dato of publication after 2015. Publications were excluded if they evaluated telehealth or used web-based software for desktop devices only. Relevant systematic reviews and the references of the research articles they contained were also searched in case that studies were missed during the initial search. Searches were made on December 17th, 2021. Two investigators independently reviewed the titles and abstracts of the identified studies and then read the full text of all selected papers. In case a discrepancy was found, it was discussed with a third investigator in order to make a final decision. The quality of the included studies was analyzed by the Cochrane Collaboration Risk of Bias Tool and the Methodological Index for Non-Randomized Studies. RESULTS Twenty-two unique studies involving 3,502 patients were included. The focus of the interventions in the studies included in the review were physical activity (11 studies), tailored information for better self-management of the disease (8 studies), mental health therapies (6 studies), symptom tracker (4 studies), and others (6 studies). All interventions were at least 8 weeks long, with a median duration of 12 weeks (interquartile range 4-18 weeks). mHealth interventions showed better results on symptom burden, fatigue, quality of life and physical activity. Likewise, tailored information, symptom tracker, nutrition and physical activity were the interventions that yielded better results. Apps with interactive support had a higher rate of positive findings, while interventions targeted to survivors showed worse results. CONCLUSIONS mHealth applications in BC patients is a highly heterogeneous field. Our study suggests that interventions focused on newly diagnosed patients or patients while on chemotherapy, interventions with interactive human support and those with a duration of 12 weeks or more showed better results in terms of patient-reported outcome. Interventions must be adapted to each patient’s characteristics and disease stage to meet their specific needs at the time of deployment. Positive impact on endpoints shows what can be achieved with the right mHealth intervention. The reproducibility of the studies reporting mHealth interventions is currently uncertain. CLINICALTRIAL PROSPERO CRD42022341598; https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022341598